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Treatment of Air Quality Data Influenced by Exceptional Events (Homepage for Exceptional Events)

Exceptional events are unusual or naturally occurring events that can affect air quality but are not reasonably controllable using techniques that tribal, state or local air agencies may implement in order to attain and maintain the National Ambient Air Quality Standards (NAAQS). Exceptional events may include wildfires, high wind dust events, prescribed fires, stratospheric ozone intrusions, and volcanic and seismic activities.

The Exceptional Events Rule

In September of 2016, the Environmental Protection Agency (EPA) finalized revisions to the Exceptional Events Rule to establish criteria and procedures for use in determining if air quality monitoring data has been influenced by exceptional events. The rule:

  • applies to all exceptional event types and all NAAQS,
  • ensures that air quality measurements are properly evaluated and characterized with regard to their causes,
  • identifies reasonable actions that state, local and tribal air quality agencies should take to address the air quality and public health impacts caused by these types of events,
  • avoids imposing unreasonable planning requirements on air quality agencies related to violations of the NAAQS due to exceptional events, and
  • ensures that the use of air quality data, whether afforded special treatment or not, is subject to full public disclosure and review.

The 2016 Exceptional Events Rule revises and replaces the 2007 Exceptional Events Rule to address issues raised by stakeholders and to increase the administrative efficiency of the Exceptional Events Rule criteria and process.

The Final 2016 Exceptional Events Rule, Supporting Guidance Documents, Updated FAQs, and Other Rule Implementation Resources

Example Demonstrations and EPA Responses Prepared under the 2016 Exceptional Events Rule

Federal Register Notices and Other Documents that Informed the Development of the 2016 Exceptional Events Rule

Electronic Submission of  Exceptional Events Demonstrations and/or Mitigation Plans

EPA Exceptional Events Contact:
Denise Scott
U.S. EPA, Office of Air Quality Planning and Standards
(919) 541-4280